2007 held the record for the most dramatic arctic ice melt ever recorded until this past hot summer, when that record fell by an area the size of texas. Many see this warming trend as part of a planetary disaster, others are more interested in the massive oil reserves, now opening up in the arctic circle. And tonight, we take you a couple dozen miles offshore from point hope, alaska, where abc's cecilia vega found the front line between sea conservation and oil exploration. Reporter: Wooly socks. Emergency radio. Check. Robotic arm, check. We're about to enter the frigid waters of the chukchi see off the coast of alaska. It's one of the most remote places on earth. But these days, it's also a battleground. There you go. All right. Reporter: Under this sea there's thought to be nearly 30 billion barrels of oil. This is amazing already. Reporter: And just a few miles from us, shell is gearing up to start drilling. They hope to strike it rich. And greenpeace hopes to stop them. It is a dangerous mission. Just me and greenpeace marine biologist john hocevar. At about 200 feet down, the world outside our sub is teeming with life. Looks like a crab. Plankton, krill, a seabed blanketed with starfish. The whole floor is covered by them. And creatures scene from another world. Whoa. It's huge. That's the biggest I've ever seen. Reporter: But hocevar says drilling could spell catastrophe for this fragile ecosystem that sustains life up the food chain. You would be talking about millions and millions of dead organisms. to be enormous. The arctic may hold a quarter of the earth's undiscovered oil, enough to drastically reduce america's dependency on foreign supplies. The oil giant has promised to drill safely and responsibly, developing new technologies to reduce drilling noise. And dedicating a fleet of vessels designed to respond to a spill in 60 minutes, 24 hours a day. Shell bent over backwards over the last five years to compromise here. Reporter: And shell has found support in some unlikely corners. Like bob reiss, an environmental writer who spent three years reporting on the battle for the arctic. I think if a company does bend over backwards, they ought to be rewarded for it. Reporter: And that reward came directly from the obama administration, which gave shell the green light to start drilling. Shell declined our request for an interview. But told us in an e-mail, the debate on whether to evaluate arctic energy resources is over. We are now focused on safe execution. But greenpeace says it's time to draw a line in the ice. They vow not to stop until all arctic drilling is banned permanently. You drill for oil, it's utter madness. Reporter: Earlier this year, activists disrupted operations on a russian rig for five days, despite being pummeled by a water canon. But in the fight against shell, greenpeace is trying a different approach, science. Theysnvited u to tagalong. It's a bumpy ride to their research hub 40 miles offshore. If you fall in this water, you could easily die within just three minutes. We're welcomed aboard "the esperanza," greenpeace's ship. And life onboard is what you might expect. Tofu for lunch, a serious recycling program and an eclectic crew from all over the world, who dedicate their lives to the cause. In this remote, unforgiving environment, we know it would be impossible to clean up an oil spill. We can't risk it. If you drop any kind of development because a spill can occur? Or do you have systems and backup systems or other backup systems to deal with a l, which shell does, and be allowed to proceed? It's a tough battle, sometimes, to choose. Reporter: For those who call the arctic home, like point hope, alaska, mayor, steve omittuk, there's no easy answers. People need money. They need our economy to come up. But we need our way of life, also. Reporter: Drilling would bring in much-needed jobs. But steve says his community would always rely on life in the sea to survive. The ocean is our garden. The animals are our identity of a people. Reporter: Pretty peaceful down here. And down below, our exploration of the arctic's underwater garden continues. There is one final discovery. It could be a coral. That is potentially a very exciting find. And away we go. Reporter: We make our way back to the surface for a closer look at the catch. First, a gargantuan starfish. Probably weighs eight pounds. Reporter: Then, what hocevar is really excited about. This may be a soft coral. If so, this would be the first specimen of coral ever collected in the chukchi sea. Reporter: Environmentalists say these creatures may offer big insight into what's at stake. We're rushing ahead to allow drilling in the arctic. And we don't even know what's down there. Reporter: Greenpeace faces an uphill battle. Shell has begun preliminary drilling. And next year looks set to be full steam ahead. I'm cecilia vegas for "nightline," off point hope, alaska.

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